1. Field of the Invention
The present invention relates to a cassette for accommodating a plurality of substrates in mutual isolation. The invention further relates to a substrate supporting rod which is to be a functional member of said cassette.
2. Description of Related Art
Substrates such as glass substrates must be stored and taken out from a cassette in such a manner that the plural substrates will not contact with each other.
The cassette in common use comprises a box-shaped resin frame equipped with pairs of opposed resin side members each formed with grooves so that one and each substrate may be accommodated between grooves of the opposed side boards.
JP H 08-021612 discloses a cassette comprising a plurality of substrate-supporting boards 2 including a body 21 and a plurality of shelf members 22 extending in parallel from the body 21 at a predetermined pitch as illustrated in FIG. 1 and FIG. 2. The shelf member 22 comprises a first shelf 22X extending inwardly of the cassette and a second shelf 22Y extending outwardly of the cassette. In addition, a projection 23 is provided on the end of the first shelf 22X of which the highest portion is smooth curve surface. Although the projection 23 for supporting a substrate B leads to a decrease of dusts of friction between edges of the substrate B and the substrate-supporting board 2, the problem of static discharge can not be solved. Otherwise, for the substrate-supporting board 2 is a structure of board, not all parts of the first shelf 22X can be used for supporting the substrate B. Therefore, it is a waste of material on design.
Referring to FIG. 3, another conventional cassette disclosed in the U.S. Pat. No. 5,584,401 has a plurality of substrate-supporting side boards 2 comprising a metal core M, an overlay 21 and a plurality of tongue-shaped shelf members 22, at least the frontal part of said overlay and the shelf members being made of resin, and at least a rib-like projection 3× extending centrally and longitudinally from the overlay being molded from a dust-inhibited resin molding material, with the remainder being molded from an electrically conductive resin molding material. Although said cassette is protected against static discharge in the insertion and removal of substrates and is not liable to form dusts such as the dust of friction due to friction against substrates, its whole structure is complex so that the cost of the fabrication is high.
Therefore, it is desirable to provide a cassette which both saves material and inhibits static discharge in the insertion and removal of substrates.